Single hung and double hung sliding sash windows are commonly used today in the construction of residential and commercial buildings. Sash locks are typically mounted to the meeting rail of the bottom sash window to lock the sash or sashes, by preventing the lower sash (or both the lower and upper sashes for a double hung window), from being opened through sliding movement relative to the master window frame. Also, in order to assist in the cleaning of the exterior of the glazing of the sash window, it may be constructed differently. Rather than the sash window frame itself being slidable within the master window frame, a lower pivotal member on the sash window may slide therein, and a pair of tilt latch devices mounted on an upper part of the window frame may also slide in the track of the master window frame. The tilt latches may be actuated to be withdrawn from the track to permit tilting of the sash window about the lower pivotal member into the room.
However, this arrangement relies solely upon the tilt latch at the top of the sliding sash window and the pivotal attachment at the bottom of the sash member to provide the structural integrity needed to resist high wind loads, since the sash frame itself is not nested within the track of the master window frame. Because of the annual threat of extreme weather at the eastern coastal areas of the U.S., particularly from hurricanes but also from macro-scale storms (a Nor'easter) that can generate hurricane force winds, these areas often mandate that the windows installed today be constructed according to very high standards. These standards may require the window to be able to structurally withstand, for a set period of time, a specified design pressure, which would permit the window to maintain its integrity throughout the sustained winds of a category five hurricane. Under such loading, it is not uncommon to see a window convex significantly, but when properly designed, the window will regain its original form. This significant deformation under such high wind loads creates a serious problem for the window hardware, particularly the tilt latch, as the latch member merely being biased into the master window frame track does not serve to resist bending. The deformation thus permitted from high wind loads may result in moisture and debris entering the interior of the dwelling through any gaps resulting from the deformation.
Another issue with respect to the design of windows for extreme weather concerns impact loading. An impact resistant sash window may include an impact-resistant glazing housed in a frame that may be securely fastened to the master window frame. The impact resistant glazing may be made of two sheets of glass laminated together, with a shatter-proof membrane between the sheets. If the exterior of the glazing is impacted by debris carried by high speed winds, the outer sheet of glass may shatter, but the inner sheet of glass is protected by the membrane, which may also serve to retain the shattered outer glass fragments in the frame. The inner sheet of glass still prevents the wind and moisture from reaching the interior of the dwelling. However, the tilt latch being unable to resist deformation may nonetheless allows debris and moisture to enter the residence through gaps resulting from such deformation, irrespective of the integrity of the impact-resistant glazing being maintained.
The present invention seeks to provide improvements to the window latch hardware in the form of an integrated sash lock and tilt latch fastener for single hung or double hung windows, which provides better resistance to wind loading and impact loading, for improved window pressure ratings.